What is "dart sac"

Dart \Dart\ (d[aum]rt), n. [OF. dart, of German origin; cf. OHG. tart javelin, dart, AS. dara[eth], daro[eth], Sw. dart dagger, Icel. darra[eth]r dart.]

1. A pointed missile weapon, intended to be thrown by the hand; a short lance; a javelin; hence, any sharp-pointed missile weapon, as an arrow.

   And he [Joab] took three darts in his hand, and thrust them through the heart of Absalom.
   --2 Sa. xviii. 14.

2. Anything resembling a dart; anything that pierces or wounds like a dart.

   The artful inquiry, whose venomed dart Scarce wounds the hearing while it stabs the heart.
   --Hannan More.

3. A spear set as a prize in running. [Obs.]
   --Chaucer.

4. (Zo["o]l.) A fish; the dace. See Dace.

   Dart sac (Zo["o]l.), a sac connected with the reproductive organs of land snails, which contains a dart, or arrowlike structure.

n. A sac connected with the reproductive organs of land snails, containing a dart, or arrow-like structure.